CentralEndpointIntersector.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2006 Refractions Research Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation. 
 * See the COPYING file for more information.
 *
 **********************************************************************
 *
 * Last port: algorithm/CentralEndpointIntersector.java rev. 1.1
 *
 **********************************************************************/
 
#ifndef GEOS_ALGORITHM_CENTRALENDPOINTINTERSECTOR_H
#define GEOS_ALGORITHM_CENTRALENDPOINTINTERSECTOR_H
 
#include <geos/export.h>
#include <geos/geom/Coordinate.h>
 
#include <string>
#include <limits>
 
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4251) // warning C4251: needs to have dll-interface to be used by clients of class
#endif
 
// Forward declarations
namespace geos {
        namespace geom {
                //class PrecisionModel;
        }
}
 
namespace geos {
namespace algorithm { // geos::algorithm

class GEOS_DLL CentralEndpointIntersector {
 
public: 
 
        static const geom::Coordinate& getIntersection(const geom::Coordinate& p00,
                        const geom::Coordinate& p01, const geom::Coordinate& p10,
                        const geom::Coordinate& p11)
        {
                CentralEndpointIntersector intor(p00, p01, p10, p11);
                return intor.getIntersection();
        }
 
        CentralEndpointIntersector(const geom::Coordinate& p00,
                        const geom::Coordinate& p01,
                        const geom::Coordinate& p10,
                        const geom::Coordinate& p11)
                :
                _pts(4)
        {
                _pts[0]=p00;
                _pts[1]=p01;
                _pts[2]=p10;
                _pts[3]=p11;
                compute();
        }
 
        const geom::Coordinate& getIntersection() const
        {
                return _intPt;
        }
 
 
private:
 
        // This is likely overkill.. we'll be allocating heap
        // memory at every call !
        std::vector<geom::Coordinate> _pts;
 
        geom::Coordinate _intPt;
 
        void compute()
        {
                geom::Coordinate centroid = average(_pts);
                _intPt = findNearestPoint(centroid, _pts);
        }
 
        static geom::Coordinate average(
                        const std::vector<geom::Coordinate>& pts)
        {
                geom::Coordinate avg(0, 0);
                size_t n = pts.size();
                if ( ! n ) return avg;
                for (std::size_t i=0; i<n; ++i)
                {
                        avg.x += pts[i].x;
                        avg.y += pts[i].y;
                }
                avg.x /= n;
                avg.y /= n;
                return avg;
        }

        geom::Coordinate findNearestPoint(const geom::Coordinate& p,
                        const std::vector<geom::Coordinate>& pts) const
        {
                double minDist = std::numeric_limits<double>::max();
                geom::Coordinate result = geom::Coordinate::getNull();
                for (std::size_t i = 0, n=pts.size(); i < n; ++i) {
                        double dist = p.distance(pts[i]);
                        if (dist < minDist) {
                                minDist = dist;
                                result = pts[i];
                        }
                }
                return result;
        }
};
 
} // namespace geos::algorithm
} // namespace geos
 
#ifdef _MSC_VER
#pragma warning(pop)
#endif
 
#endif // GEOS_ALGORITHM_CENTRALENDPOINTINTERSECTOR_H